Nutrition challenges continue throughout the life cycle, as
depicted in Figure 1.1. Poor nutrition often starts in utero and extends,
particularly for girls and women, well into adolescent and adult life. It also
spans generations. Undernutrition that occurs during childhood, adolescence, and
pregnancy has an additive negative impact on the birthweight of infants.
Low-birthweight (LBW) infants who have suffered intrauterine growth retardation
(IUGR) as foetuses are born undernourished and are at a far higher risk of dying
in the neonatal period or later infancy. If they survive, they are unlikely to
significantly catch up on this lost growth later and are more likely to
experience a variety of developmental deficits. A low-birthweight infant is thus
more likely to be underweight or stunted in early life.

The consequences of being born undernourished extend into
adulthood. Epidemiological evidence from both developing and industrialized
countries now suggests a link between foetal undernutrition and increased risk
of various adult chronic diseases - the foetal origins of disease
hypothesis.1

Source: Prepared by Nina Seres for the
ACC/SCN-appointed Commission on the Nutrition Challenges of the 21st
Century.

During infancy and early childhood, frequent or prolonged
infections and inadequate intakes of nutrients - particularly energy, protein,
vitamin A, zinc, and iron - exacerbate the effects of foetal growth retardation.
Most growth faltering, resulting in underweight and stunting, occurs within a
relatively short period - from before birth until about two years of
age.

Undernutrition in early childhood has serious consequences.
Underweight children tend to have more severe illnesses, including diarrhoea and
pneumonia. There is a strong exponential association between the severity of
underweight and mortality.2 It has been estimated that out of 11.6
million deaths that occurred in 1995 among children under five in developing
countries, 6.3 million (54%) were associated with low weight-for-age. The
majority of these deaths can be attributed to the potentiating effect of mild to
moderate undernutrition.3

The nutrition and health of school-age children in developing
countries have only recently begun to receive attention. A long-standing
assumption has been that by school age a child has survived the most critical
period and is no longer vulnerable. However, many of the infectious diseases
affecting preschool children persist into the school years. Until recently, data
on the nutritional Status of school-age children were not routinely collected,
despite growing evidence, first, that malnutrition was widespread in this age
group, and second, that these nutritional problems adversely affect school
attendance, performance, and learning.

In adolescence, a second period of rapid growth may serve as a
window of opportunity for compensating for early childhood growth failure,
although the potential for significant catch-up at this time is limited. Also,
even if the adolescent catches up on some lost growth, the effects of early
childhood undernutrition on cognitive development and behaviour may not be fully
redressed.4 A stunted girl is thus most likely to become a stunted
adolescent and later a stunted woman. Apart from direct effects on her health
and productivity, adult stunting and underweight increase the chance that her
children will be born with low birthweight. And so the cycle turns.

It is imperative to prevent foetal and early childhood
undernutrition. Nutrition interventions in pregnancy and early childhood can
result in improvements in body size and composition in adolescents and young
adults. Improvements in both physical and intellectual performance were also
found in a study by the Institute for Nutrition for Central America and Panama
(INCAP).5

Investing in maternal and childhood nutrition will have both
short - and long-term benefits of huge economic and social significance,
including reduced health care costs throughout the life cycle, increased
educability and intellectual capacity, and increased adult productivity. No
economic analysis can fully capture the benefits of such sustained mental,
physical, and social development.

The life cycle provides a strong framework for discussing the
challenges facing human nutrition. Although information is available on
preschool children in most regions, the paucity of data for other age groups
precludes sub-regional and regional descriptions of the nutritional problems
faced at these periods of the life cycle.

The causes of malnutrition are complex. Underlying the
immediate causes of malnutrition will be a failure of either the main food,
health, or care preconditions for good nutrition. The widely used
food-health-care conceptual framework, shown in Appendix 1, offers an analytical
tool for portraying causes of malnutrition and is used throughout this
report.

For the most part, the results in this Fourth Report
are presented according to the regions and sub-regions defined by the United
Nations Population Division. A listing of the countries within each sub-region
is provided in Appendix 2. These sub-regions are different from those used by
the ACC/SCN since 1987. The objective of this change is to help standardize the
use of common regions and sub-regions among UN agencies. WHO began to use this
classification in 1993. Data described in this chapter derive from stable
national populations. The nutritional status of refugees and internally
displaced populations is described in Chapter 5.